In photolithography, critical dimension (CD) is the minimum features size that is to be patterned on the wafer or the minimal distance between adjacent features. The features can be lines, rectangles, elliptical or other shapes with any orientation, e.g. vertical, horizontal or other.
Critical dimension scanning electron microscopes (CD-SEM) are used to measure critical dimensions of such features by scanning an area of the wafer that includes such features with an electron beam to provide a SEM image. The SEM image is then processed by applying an edge detection process in order to detect edges of the features and to detect the distance between these edges.
Many prior art edge detection processes are based upon the assumption that the electron beam is much narrower than the width of the scanned lines therefore the interaction volume size created is such that each line should be represented by two clear edges.
Modern manufacturing process managed to shrink the dimensions of features and the electron beam is no longer much narrower than the width of the scanned lines.
There is a growing need to provide an accurate system, method and computer readable medium for edge detection.